IDRIS Elba is one of Hollywood's go-to leading men, able to effortlessly shift between drama, romance and action.

But in a new and very different role, the Golden Globe and SAG Award winner enters the ring for the most physically and mentally demanding experience of his career - training to become a professional kickboxer and compete against a seasoned fighter in a no-holds-barred bout.

Cameras follow the father-of-two as he travelled to Cuba, Japan, South Africa and Thailand to train with the best coaches and fighters in the world.

British actor Idris Elba arrives at the Rafael Trejo boxing gym in the Old Havana section of Havana, Cuba for a boxing workout. Angel Valentin

During the year-long process of becoming "fight ready" Elba also continued his day job, working two major films: The Dark Tower and, in Australia, Thor: Ragnarok.

"As long as I didn't spar or, you know, damage my face, then I was fine. But I didn't give them a choice to say whether I can do it or not," he says.

"I was already doing it by the time I got onto both those films. I was respectful of the requirements of my day job. I didn't want to jeopardise any filming or any budgets by being silly and sparring and hurting myself. So, I just trained at those times with extreme fitness training, which helped for both because they were very extreme films."

But he promises there's no acting when he puts on the gloves.

"Skilful actors do a really good job of convincing the audience that they are professional at whatever the character is," he says. "So, of course when I was training, I had to think like a fighter.

"This is one of the biggest, weirdest characters I've ever played because it's not a script. It's actually me, but I am using the skill set as an actor to make it as real as possible. I mean, the truth is, though, when you get punched in the face, or you get kicked in your leg and it hurts, there is no acting there."

Idris Elba warms up before his first fight at the Repton Club in London in a scene from the TV series Idris Elba: Fighter. Contributed

The 44-year-old, who overcame a back injury to continue his kickboxing training, hopes his documentary inspires viewers to find their own mountains, figurative or literal, to climb.

"I think people can take away that if someone says you can't do something, that doesn't actually mean you can't do it. People might hopefully take away some sort of inspiration of challenging themselves," he says.

"I push myself a little bit more because of the training that I went through.

"I'm doing a film at the moment, which is pretty challenging, and I go 'Okay, I can do better'... I realised I'm not doing what I was doing in kickboxing, which was so much harder. So as an actor, I can push myself even further now I think, or I want to."

Idris Elba: Fighter premieres on Tuesday at 9.30pm on the Discovery Channel.